A typical disc drive includes a rigid housing that encloses a variety of disc drive components. The components include one or more rotating discs having data surfaces that are coated with a medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor that causes the discs to spin and the data surfaces of the discs to pass under respective aerodynamic bearing disc head sliders. Sliders carry transducers which write information to and read information from the data surfaces of the discs.
Typically, transducers or heads include an inductive recording or write head for generating a magnetic field that aligns the magnetic moments of the recording layer of a magnetic medium to represent desired bits of data. In addition, transducers include a read element that is configured to read magnetic flux transitions recorded to data tracks on the medium which represent the bits of data. The magnetic flux from the recording medium causes a change in the electrical resistivity of the read element, which can be detected by passing a sense current through the read element and measuring a voltage across the read element. The voltage measurement can then be decoded to determine the recorded data.
Magnetic recording heads include both longitudinal and perpendicular recording techniques. Perpendicular recording is a form of magnetic recording in which magnetic moments representing bits of data are oriented perpendicularly to the surface of the recording layer of the recording medium, as opposed to longitudinally along a track of the medium as in the more traditional longitudinal recording technique.
Perpendicular magnetic write heads typically include main and return poles that are separated by a non-magnetic spacer. The main and return poles each extend from pole tips located at an air-bearing surface (ABS) to a back gap region. A back gap closure typically connects the main and return poles together at the back gap region to form a magnetically conductive path therebetween. A coil typically surrounds the back gap closure and is used to generate magnetic signals through the main and return poles in response to a current conducted therethrough. The magnetic signals are focused at the main pole tip such that they interact with a recording layer of a magnetic medium to orient its magnetic moments in an up or down direction. The return pole, however, even in the absence of current flowing through the coil, can generate an erasure field that could inadvertently erase or write over previously written data on the magnetic medium by reorienting magnetization in data patterns. Thus, a need exists to reduce these undesirable erasure effects.